Patient ventilator apparatus

ABSTRACT

Disclosed herein is a patient ventilator apparatus having a pneumatic control system operable in three different modes wherein the apparatus assists the breathing of the patient, controls the patient&#39;&#39;s breathing in a timed manner, or operates in a combination assist/control mode according to certain predetermined conditions. Fluidic circuitry controls a valved bellows apparatus, which in turn supplies air to a patient subject to limitations of time, volume, and pressure, wherein the gas supplied to the bellows comprises an adjustable oxygen/air mixture. Fluidic timers are provided for use in the control mode of the circuitry, and identical fluidic circuitry combinations are provided for use in the assist mode to automatically trigger the ventilator apparatus into an inspiratory state according to the patient&#39;&#39;s breathing requirements and to trigger such apparatus into an exhalation state when a predetermined inspiratory pressure is attained.

A United States Patent 1191 Russell Nov. 4, 1975 PATIENT VENTILATORAPPARATUS [57] ABSTRACT [75] Inventor: George K. Russell, Castle Rock,

Colo' Disclosed herein is a patient ventilator apparatus hav- [73]Assignee: Sandoz, Inc., E. Hanover, NJ. ing a pneumatic control systemoperable in three different modes wherein the apparatus assists thebreath- [22] Flled' Sept' 1973 ing of the patient, controls the patientsbreathing in a PP 401,739 timed manner, or operates in a combinationassistlcontrol mode according to certain predetermined [52] U S C]128/145 8 conditions. Fluidic circuitry controls a valved bellows In}.Cl .2 pp in turn ppli i t a ti nt ub- [58] Field of Search 128/1458,145.7, 145.6, hmtatms "i volume and prissure 128/1455 142 188 whereinthe gas supplled to the bellows compnses an ad ustable oxygen/a rm1xture. FluldlC timers are pro- [56] References Cited vided for use inthe control mode of the circuitry, and identical fluidic circuitrycombinations are provided UNITED STATES PATENTS for use in the assistmode to automatically trigger the 3,669,108 6/ 1972 Sundblom 128/ 145.8ventilator apparatus into an inspiratory state accord- 373O1180 5/ 1973f f 128/145-3 ing to the patients breathing requirements and to trig-3,754,550 8/1973 Kipling 128/1458 Such apparatus into an exhalationstate when a 3,756,229 9/1973 Olliver 128/1458 Primary ExaminerRichardA. Gaudet Assistant ExaminerHenry J. Recla Attorney, Agent, orFirmGerald D. Sharkin; Robert S. Honor; Walter F. Jewell MEZWEQ MODE 7oSWITCH FILTER predetermined inspiratory pressure is attained.

10 Claims; 9 Drawing Figures 5 p 9 OXYGEN mss PATIENT PRESSURE GUAGEPATIENT REE LINE INSFIRv TIMER I E RATIO REE suns: sen; wmr 78 116511;wnzssunz 4 LIMIT I l i "4 Fur POWER 5g VALVE OXYGEN mar e MIA 92 sowmca'ron PATIENT nmvsn /\TRIGGER mxms DEVICE 3 52 A FILTER I has?NEBgkIZATION 4 Q PATIENT HOSE T0 EXHALATION VALVE on PATIENT Q VOLUME LIMIT U.S. Patent Nov, 4, 1975 Sheet 1 0f 6 3,916,889

U.S. Patent Nov. 4, 1975 Sheet2 of6 3,916,889

I U.S. Patent Nov. 4, 1975 Sheet3of6 3,916,889

US. Patent Nov.4, 1975 Sheet40f6 3,916,889

US. Patent N0v.4, 1975 SheetS 0f6 3,916,889

US. Patent Nov. 4, 1975 Sheet6of6 3,916,889

FIG. 7

FIG. 9

PATIENT VENTILATOR APPARATUS BACKGROUND OF THE DISCLOSURE Certainrespiratory apparatus is known in the art wherein fluidic circuits areprovided for controlling the exhalation and inhalation cycles of apatient. However, the instant disclosure relates to an improved patientventilator apparatus utilizing totally pneumatic control circuitry foroperating the ventilator apparatus in a plurality of desired modeswherein the breathing of the patient is assisted, completely controlled,or subjected to a combination assist/control operation according topredetermined parameters.

SUMMARY OF THE INVENTION In accordance with the invention there isprovided a pneumatic ventilator apparatus utilizing a pressurized sourceof gas for operating fluidic circuitry, which in turn controls a sourceof gas supplied to a patient. During the inspiratory cycle air isexhausted from a bellows apparatus, and supplied through an outlet valueto a patient breathing hose. The bellows is surrounded by a confinedvolume, and it is evacuated by supplying oxygen to that confined volume,thus causing the bellows to collapse. A weight is provided in the freelower end of the bellows, so that upon release of the oxygen pressure inthe confined area surrounding the bellows, the latter will automaticallybe exposed under the influence of the weight, thereby pushing the oxygenout from the confined area and through a mixing valve, wherein theoxygen is either vented to the atmosphere or mixed with a supply of roomair and then injected into the expanding bellows for use in the nextsucceeding inhalation cycle. An inlet valve couples the mixing valve tothe confined volume surrounding the bellows, and the inlet and outletvalves for the bellows apparatus are actuated alternately during theexhalation and inhalation cycles, respectively, by means of a logiccircuit having its input coupled to one output of a master flip flopwhich in turn is controlled at one input by an exhalation timer signaland an automatic patient trigger signal, and controlled at its otherinput side by an inspiration timer signal, a pressure limit triggeringcircuit signal, and a volume limit signal coupled from the bellowsapparatus.

The ventilator apparatus is provided with three different modes ofoperation selectable by means of a manually operable pneumatic switch.First, in an AS- SIST mode the selecting switch is connected to activatethe patient trigger circuit which, together with the pressure limitcircuit, is responsive to the air pressure in a patient reference line,so that the master flip flop switches states to control the exhalationand respiration cycles of the bellows apparatus in accordance with thepatients breathing demands. That is, when the air pressure in thepatient reference line drops to a low level indicating the completion ofan inspiratory cycle, that low level pressure is detected by the patienttrigger circuit which then triggers the master flip-flop to initiate theinspiratory cycle of the bellows apparatus. Then, during the ASSIST modethe pressure limit circuit provides a trigger signal to the masterflip-flop to terminate the inspiratory cycle if the pressure in thepatient reference line exceeds a predetermined value, while the volumelimit detector device in the bellows apparatus also provides a triggersignal to the master flip-flop to terminate the inspiratory cycle aftera predetermined maximum amount of air has been supplied to the patientfrom the bellows apparatus, or a fluidic timing device provides atrigger signal to the master flip-flop to terminate the inspiratorycycle after a predetermined amount of time. Therefore, the first one ofthe pressure, volume, or time signals to reach its predetermined maximumvalue is the signal which triggers the flip-flop to terminate theinspiration cycle; and the command from the patient trigger circuitterminates the exhalation cycle.

When the manually operable mode switch is positioned to select a CONTROLmode, the exhalation timer is activated and the patient trigger circuitis deactivated, so that the master flip-flop is controlled at one inputby the output of the exhalation timer, while it is controlled at itsother input by the pressure limit circuit, the inspiration timer, andthe volume limit detector. Accordingly, in the CONTROL mode theexhalation cycle is automatically timed, as is the inspiration cycle,but the latter is also terminated prematurely of the inspiration timeroutput if the pressure limit signal or volume limit signal reach theirpredetermined maximum values.

The bellows for supplying air to the patient has an adjustable volumewhich is determined by a movable plate positioned to control theexpansion of the bellows and which also contributes to defining theconfined volume surrounding the bellows. During the inspiration cycle,the master flip flop controls a power valve which supplies oxygenunderpressure to the confined volume thereby causing contraction of thebellows. Then, upon releasing the pressure in the confined volume, thebellows starts to expand under the force of a weight carried therein andthe oxygen is forced out of the confined area and through the inletvalve which is actuated to an open condition by the logic circuit. Amixing valve which receives the oxygen from the inlet valve isadjustable to conduct a controlled amount of the oxygen through to thebellows along with a partial supply of filtered room air. The room airis received at ambient pressure and is drawn into the bellows due to avacuum caused by its expansion. However, the oxygen is supplied underpressure as a result of its forced expulsion from the confined area sothat the mixing valve permits the oxygen content of the gas supplied tothe bellows to be varied from 2l-l00%.

Each of the timer devices comprises a bellows housed within a chamberhaving an input orifice for receiving oxygen at a predetermined pressureto cause a timed contraction of the bellows. A shaft has one end fixedto the movable end of the bellows, while the opposite end of the shaftcloses a vent on a back pressure detector which is coupled to the inputof the master flip-flop. Therefore, a pair of opposed inputs to themaster flipflop are controlled respectively by the movable shafts on thetwo timer bellows. Furthermore, each of the chambers surrounding thetimer bellows have dump valves mounted therein, such valves beingactuable by opposed outputs of the master flip-flop, so that as soon asthe back pressure detector of one of the bellows provides an output forswitching the master flip-flop, the resultant output of the flip-flop iscoupled back to that bellows chamber to cause its depressurization, andto prepare it for its next timing cycle. The two bellows devices andtheir surrounding chambers are mounted side by side and their backpressure sensing elements are movable mounted movably springs, so thatthey are adjustably positioned by means of a pair of cams fixed on ashaft, so that rotation of the shaft causes movement of the cams andadjustable movement of the two sensing devices. Thus, this movement ofthe sensing devices changes the timing periods for both the exhalationand inspiration timers which can be adjusted in unison by rotation ofthe shaft. Furthermore, a by-pass valve is provided in parallel with theinput orifice to the inspira-.

tion timer, and that by-pass valve can be opened to decrease theinspiration time, thus adjusting the inspiration/exhalation (I/E timeratio. However, the timing devices are constructed so that the I/E ratiohas a maximum value of unity.

The patient trigger circuitry, and the pressure limit circuit haveidentical configurations, and each comprises a more universal triggercircuit for automatic operation in a patient ventilator. In particular,the universal trigger circuit consists of a six-gate fluidic circuithaving three proportional amplifiers connected in series with each otherand with three serially connected fluidic flip-flops. In accordance withthe invention the universal circuit can be used as the patient triggerand the pressure limit circuit as described above, and depending on theinput connections thereto it can function to provide an output inresponse to a small differential pressure at its inputs; it can functionto provide an output in response to pressures slightly below ambient, aswould be caused by a patients breathing efforts; it can function toprovide an output in response to pressure levels above or belowatmospheric, wherein the device is automatically biased so that it canbe used in conjunction with end expiratory pressure signals; it canfunction to provide an output in response to air pressure inputsindicating maximum levels; and it can function to provide an output inresponse to flow signals, or rate of change of pressure as is sometimesdesirable.

In accordance with the use of the universal trigger circuits, ascontrolled in part by end expiratory pressure signals, the circuit isutilized to provide an output in response to small differentialpressures. To allow the Positive End Expiratory Pressures (PEEP) to beused during assisted breathing, without the need for the patientsinhalation effort to return the patient hose to ambient pressure, thePEEP pressure is fed through a diaphragm valve to the patient triggermodule, to bias that module so that it can be triggered while thepatient reference line is still above the ambient pressure level.

BRIEF DESCRIPTION OF THE DRAWINGS One embodiment of the invention isdescribed herein in conjunction in the accompanying drawings. In suchdrawings:

FIG. I shows a block diagram of a patient ventilator apparatus accordingto the invention;

FIG. 2 is a schematic view of the fluidic circuitry illustrated in FIG.1;

FIG. 3 is a front elevation of the mixing device mounted on the bellowsapparatus disclosed in FIG. 1;

FIG. 4' is a sectional view taken along the line 4-4 of FIG. 3;

FIG. 5 is a sectional view taken along the line 55 of FIG. 3;

FIG. 6 is a sectional view taken along the lines 66 of FIG. 3;

FIG. 7 is a perspective view of the mixer valve stem illustrated inFIGS. 3-5;

FIG. 8 is a sectional view of the timer devices illustratedschematically in FIG. 2; and

FIG. 9 is a sectional view of a dump valve used with the timer devicesof FIG. 4.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION:

An embodiment of the invention is depicted in block diagram form in FIG.1 of the drawings, and includes a bellows apparatus 10 having a bellowselement 12 fixedly held at its upper end within a cylindrically formedchamber 14. The chamber 14 is provided at its upper end with aconnecting conduit 16, and is provided at its lower end with anadjustable plate 18 having a seal 20 connected at its periphery forsealing the plate against the sidewalls of the chamber 14. The plate isadjustably movable through the chamber 14 by means of an adjustingdevice 15, so that when the plate is moved upwardly the confined volumeof the chamber within which the bellows can expand and contract isdecreased, while such volume is increased when the plate 18 is moveddownwardly within the chamber 14. In operation, the bellows element 12is charged with air through an input duct 22 having a check valve 24mounted thereon, and the bellows element is connected in communicationwith an outlet valve 26 for actuation to allow air within the bellowselement to be discharged to the patient during the inspiration cycle.The discharge of air from the bellows element 12 is effected bypressurizing the chamber 14 with oxygen supplied through the conduit 16.When the chamber 14 is so pressurized with oxygen, it causes the bellowselement 12 to collapse to expel the air previously charged therein.

Accordingly, the tidal volume of the system is determined by theplacement of the plate 18 which plate also minimizes gas consumption bylimiting the confined volume surrounding the bellows element 12. Asillustrated, the check valve 24 closes off the input port to the bellowselement during its collapse. The output valve 26 also includes a checkvalve to prevent air from the patient hose 28 from being injected intothe bellows element, and the valve 26 is controlled by a diaphragm 30,which in turn is controlled by the fluidic circuitry described below.

The bellows element 12 continues its collapsing movement until thechamber 14 is depressurized in response to one of four different controlsignals which are adapted to terminate the inspiration cycle. One ofthese four control signals is initiated by a rod 32 mounted above thebellows element 12 and spring loaded in a downward direction, butmovable upwardly due to pressure exerted by the upward movement of thelower portion of the bellows element wherein such upward movement of therod indicates the total exhaustion of the air previously charged intothe bellows element. The rod 32 closes a vent in a pressurized conduit34, thus providing a back pressure signal along a volume limit conduit36. The conduit 34 is pressurized by a regulated supply of oxygen fedthrough an orifice 37.

As stated above, the inspiration cycle is terminated when the chamber 14is depressurized, and at that time the bellows element 12 automaticallyexpands under the force of a weight 38 housed in its lower extremity. Asthe bellows element expands it creates a partial vacuum which opens theinlet check valve 24 and draws air inwardly through the conduit 22 whichhas a filter 40 connected thereto and disposed in communication withroom air. Depressurization of the chamber 14 is obtained by opening abellows inlet valve 42 so that the oxygen which is forced out of thechamber 14 by the expanding bellows element 12 is coupled through theinlet valve 42 to a three port mixing valve 44 as described in detailbelow in conjunction with FIGS. 37. In operation, the oxygen dischargedfrom the chamber 14 through the valve 42 is vented to atmosphere by thevalve 44, or is directed in an adjustablycontrolled volume to theconduit 22 which supplied air to the bellows element 12. Since theoxygen is discharged under pressure from the chamber 14, due to theexpansion of the bellows element 12, the pressure of the oxygen exitingthe mixer valve 44 is greater than the ambient pressure of the room aircoupled through the filter 40, and therefore the oxygen/air mixture canbe varied by positioning the valve 44 to a desired position.

The input and output valves 26 and 42 of the bellows apparatus 10, andthe supply of oxygen to the chamber 14, are controlled by the fluidiccircuitry shown in block diagram form in FIG. 1, such circuitry beingenergized by a 50 psig oxygen supply source indicated at referencenumeral 46. The pressurized oxygen is cou pled through a filter 48 to apower valve 50 which is gated to supply oxygen through an adjustableflow valve 52, and through a silencer-filter 54 to the input conduit 16for the bellows chamber 14. The output of the filter 48 is also coupledto a regulator 56 wherein the oxygen pressure is reduced so that theoxygen emanating from the regulator 56 can be used as a supply sourcefor the active elements of the fluidic circuitry. The regulated oxygen,which may be at a pressure of about 5 psig, is also coupled through athree position mode selector switch 58, which permits the selection ofthree modes of operation, including an ASSIST mode, a CONTROL mode, andan ASSIST/CONTROL mode.

The fluidic circuitry includes a master flip flop 60 having a principleoutput 62 which actuates the power valve 50, and which operates a dualOR/NOR circuit 64 to provide regulated oxygen pressure signals along therespective conduits 66 and 68 to the inlet and outlet valves 42 and 26of the bellows apparatus 10. In partic ular, when the output 62 of theflip flop 60 provides a positive pressure, the dual OR/NOR circuitprovides a positive signal on the output conduit 66 to close the inletport to the bellows apparatus, while the outlet port 26 is allowed toopen so that the inspiration cycle will commence due to collapsingmovement of the bellows element 12, which in turn results frompressurization of the chamber 14. Similarly, upon completion of theinspiration cycle, the flip flop 60 will switch to its opposite stablestate whereby a positive regulated pressure signal will be coupled alongconduit 68 to close the outlet valve 26 while the pressure on conduit 66will be decreased to allow the valve 42 to open so that he oxygendischarged from the bellows chamber 14 will pass through that inputvalve 42 to the mixing valve 44.

The flip flop 60 has three inputs which cause it to switch to itsinspiration command state wherein it provides an output to conduit 62,and those three inputs are supplied from a manually operable inputsignal device 70, a patient trigger device 72, and an exhalation timerdevice 74. On the other hand, the flip flop has four inputs for causingit to terminate its inspiration command, and those inputs are coupledfrom a manually operable exhalation triggering device 76, a pressurelimit circuit 78, an inspiration timer device 80, and the volume limitdetector device formed by the elements 32, 34, and 36 disposed in thebellows apparatus 10. A pressure limit display device 82 is actuable toexhibit a red display in response to an indicator signal from a driverdevice 84 which in turn is energized by the output of the pressure limitcircuit 78. The display device 82 utilizes reflected light. Similarly, ared display device 86 is operated by a driver 88 in response to anoutput from the inspiration timer 80, while a green display light 90operates in a similar manner under the control of an indicator driver 92which is energized by an output from the patent trigger circuit 72.

In the operation of the circuitry, when the ASSIST mode is selected, aregulated oxygen pressure signal is applied to the patient triggercircuit through a conduit 93 to put it in an energized condition, and aninput con trol port for the patient trigger circuit is coupled through apatient reference line 94 to the patient hose line 28, so that thepatient trigger circuit provides an output to switch the master flipflop 60 to its inspiration state when the pressure in the patientreference line 94 decreases to a minimum indicating the completion of anexhalation cycle, While the system is operating in its ASSIST mode, thegreen light 90 will be actuated at each instance of a patient triggeroutput signal, which in turn is controlled by the patients breathing inresponse to a signal coupled along the patient reference line 94.

An additional input to the patient trigger device 72 includes aregulated oxygen signal coupled through an adjustable input port 96 tocontrol the sensitivity of the trigger device 72, and an input signalfrom a Positive End Expiratory Pressure (PEEP) 98, wherein the patienttrigger device 72 is adaptable to provide an output in response to asmall differential input pressure between the input coupled along theconduit 94 and the PEEP input. The PEEP circuit 98 has a gate inputcoupled from an output conduit 100 of the dual OR/NOR circuit 64, andthe gate is maintained in a closed condition by the positive regulatedoxygen supply coupled through a small orifice 102, an adjustable orifice104, and a one way valve 106, to the gate input, wherein the junction ofthe adjustable orifice 104 and the one way valve 106 are vented to theatmosphere through an orifice 108. However, during an exhalation cycle,the pressure in the conduit 100 opens the PEEP driver circuit to permitthe regulated pressure coupled through the orifices 102 and 104 to beapplied though an offset adjust orifice 110 and a spike dampingvolumetric chamber 112 to the patient trigger device 72.

The pressure limit circuit is identical in construction to the patienttrigger circuit, but provides an output in response to a high pressuresensed on the patient reference line 94, and the sensitivity of thedevice is adjustable by means of a variable orifice 114 coupled as asecond input thereto. Also, a pressure gauge 116 is connected at thesecond input to the pressure limit circuit 78 for displaying theselected pressure limit adjustment to which the circuit is sensitive,and a second pressure gausge 118 is connected to the patient referenceline so that the actual pressure such line can be monitored. Anadjustment is provided but not shown in FIG. 1 wherein the periods ofthe exhalation timer and the inspiration timer can be simultaneouslyadjusted, and an adjustable orifice 120 is provided in the input line tothe inspiration timer, so that the inspiration/exhalation (I/E) ratiocan be adjusted. These adjustments are desireable since medicalventilation systems require a matching of the I/E ratio to the needs ofindividual patents, and since it is usually considered detremental touse I/E which is greater than unity. Also, controlled breathing requireduniform cycle rates, but such rates should be adjustable to permitchanges in the minutevolume, without disturbing the selected I/E ratio.The above-mentioned controls satisfy these requirements.

An additional function of the ventilator apparatus disclosed herein isprovided by a conduit 122 for coupling to a nebulizer device whereinthat conduit 122 is connected through an adjustable orifice 124 to anOFF position, an INTERMITTENT position wherein the nebulizer is operatedby the output of the power valve 50, and a CONTINUOUS position whereinthe nebulizer is operated by the supply source of oxygen as coupledthrough an orifice 128.

In summary, in the ASSIST mode the inspiration cycle is terminated bythe pressure limit circuit 78, by the manually operable signal device76, by the volume limit signal coupled along the conduit 36, or by theinspiration timer 80, and the exhalation cycle is termi nated by thepatient trigger circuit 72, or the manually operable signal device 70.

In the CONTROL mode the regulated oxygen supply is coupled throgh theselecting switch 58 to energize the exhalation timer, while the patienttrigger circuit 72 is deenergized. Therefore, in the CONTROL mode theinspiratory command generated in the conduit 62 is initiated by theexhalation timer 74 or the manual signal device 70, while theinspiratory cycle is terminated by any one of the four inputs to themaster flip-flop 60 from the manually operable device, such inputsincluding signal pressure limit circuit 78, the inspiratory timer 80, orthe volume limit signal conducted along conduit 36. During normaloperation of the CONTROL mode, the master flip-flop may be operatedduring both the inspiratory and exhalation cycles in a timed mannerdetermined by the timers 74 and 80, respectively. However, theinspiratory cycle is terminated prematurely of its timed duration ifeither pressure limit or the volume limit exceeds its maximumpredetermined value.

Then, in the ASSIST/CONTROL mode, the selector switch 58 energizes boththe patient trigger circuit 72 and the exhalation timer 74 through theuse of a pair of one way valves 58A and 58B, so that the circuitryoperates as described above with respect to the CON- TROL mode with theexception that flip-flop 60 will be triggered to generate itsinspiratory command along conduit 62 by the patient trigger signal fromthe device 72, as well as by the exhalation timer 74.

The actual circuitry included in the blocks of FIG. 1 is shown ingreater detail in FIG. 2, wherein a preferred form of the patienttrigger circuit 72 is shown as comprising a six section fluidic deviceincorporating three proportional amplifiers 130A, 130B, 130C, connectedin series with each other and in series with three serially connectedflip flops 132A, 132B, 132C. Each of the six circuits has its supplyinput coupled along the conduit 73 to the mode selector switch 58 whileeach of circuits 130B, 130C, 132A, 1328, and 132C, have their controlinputs coupled to the respective outputs of the preceeding stage; whilethe control inputs to the first proportional amplifier 130A are coupledrespectively to the output of the PEEP circuit 98 and to the patientreference line 94. Furthermore, the adjustable sensitivity orifice 96 iscoupled to a second control input to the proportional amplifier 1308,and this configuration permits a stable sensitivity adjustment from +1to more than l0 cm H O with respect to ambient pressure. The fourthinput to the amplifier 1303 is vented. The gating device for the PEEPdriver 98 which is shown schematically in FIG. 2 comprises a diaphragm134 which closes off the conduit leading to the PEEP input for theproportional amplifier 130A, and it is seen that the PEEP driver 98 ismaintained in a closed condition by that diaphragm 134 due to pressurefrom conduit 100 during inspiration. The pressure through the one wayvalve 106 is negated by a signal from the dual OR/- NOR circuit 17during the inspiration cycle. Diaphragm 134 permits oxygen flow'from thevalves 102 and 104 and then through the adjustable valve and the dampingchamber 112 through to the proportional amplifier A during exhalation.Also, during exhalation the pressure through 106 is delivered to conduit100 where it is used to hold the patient circuit exhalation valve at thePEEP pressure.

In operation, an end expiratory pressure which remains higher thanambient pressure is generated by bleeding a small amount of the drivinggas into the exhalation exhaust line through the one way valve 106. Thiskeeps the diaphragm 134 of the PEEP device 98 at a slight positivepressure. Then, since most exhalation valves hold patient hose pressuresslightly higher than their actuation pressures, the OR/NOR outputpressure with PEEP will usually be less than the PEEP pressure shown onthe patient pressure gauge. Therefore, variations in the obtainable PEEPpressures will be experienced with exhalation manifolds of differentmanufacturers. To allow PEEP to be used during assisted breathing,without the need for the patients inhalation effort to return thepatient hose to ambient conditions, the PEEP pressure is fed to thepatient trigger module to bias that module so that it can be triggeredwhile the patient hose pressure is still above the ambient pressurelevel. The amount of pressure differ ence required to switch the triggermodule is preset by the offset-adjust valve 110. During inspiration, thediaphragm 134 is closed to remove the bias signal from the patienttrigger module so that high exhalation valve pressures will not hold theventilator in an inspiration condition. However, during exhalation, thediaphragm 134 opens and allows the PEEP pressure to reach the patienttrigger module circuit 130A. The system is ususally preset so that thepressure difference required to trigger the patient trigger module isrelatively large as compared to that normally required without PEEP tocompensate for leaks. The offset-adjust valve 110 is provided tofunction as a leak compensator for desensitizing the patient triggermodule during PEEP operation. I

The pressure limit circuit 78 is identical to the abovedescribed patienttrigger circuit 72 in its construction, with the exception that thesource supplied for each of the six individual circuits is coupled tothe regulated source of oxygen provided at the output of the regulator56, while the control inputs to the pressure limit circuit 78 are asdescribed above in conjunction with FIG. 1.

It is seen, therefore,that the circuits 72 and 78 as illustrated in FIG.2' of the drawings are identical, although their input signals may beconnected in different ways to make the circuit responsive to differentinput parameters. In addition to the responses described above withrespect to FIG. 2 of the drawings, the inputs to the six-state circuitcan be coupled in at least three different configurations so that thecircuit may be described as a universal trigger circuit. In this regard,for example, the inputs can be connected as illustrated at 72 in FIG. 2,while the PEEP input is replaced by an ambient pressure input so thatthe circuit will be sensitive to small negative pressures. As anotherexample, the PEEP input to the circuit 72 as illustrated in FIG. 2 maybe connected to be automatically biased to allow triggering at pressurelevels above or below atmospheric pressure. For example, the input maybe connected to a three-position switch so that when PEEP pressures areused, a pressure slightly above atmospheric is applied, while withnegative endexpiratory pressures (NEEP), a pressure slightly belowatmospheric is applicable through a second position of the switch. Insuch NEEP applications, the referenceadjust gas is used to drive aventuri for evacuating the patient hose, thereby generating the vacuumnecessary for the negative bias. The third position of the switch mayprovide for normal operation so that the universal trigger circuit maybe switched from NORMAL, to PEEP, to NEEP without requiring readjustmentof the sensitivity control. A further example of the responsiveness ofthe universal circuit results when a suitable restriction is placed inthe patient hose input, while a feedback connection is coupled to thecircuit 72 in place of the PEEP input so that the ventilator will becycled as a function of flow, or as a function of the rate of change ofpressure. That is, the feedback connection can be used to sense flowsince the pressure differential across the restriction in the patienthose will give an indication of such flow. This last-describedconfiguration can be used to turn on the ventilator due to a slightpatient breathing effort, and if a time delay circuit such as a fluidicRC circuit is provided in a parallel feedback line, the patient triggersignal can be extended.

The OR/NOR circuit 64 is also depicted in schematic form in FIG. 2 andcomprises a two stage device, wherein the first stage 136 provides apositive pressure output along the conduit 66 in response to an inputsignal received from the flip flop 60 along the conduit 62. Similarly,the second stage 138 provides an output along conduit 100 during theinspiration cycle to maintain the exhalation valve on the patient hosein a closed condition during such inspiration cycle.

In the past, fluidic timers for respiratory equipment have beenconstructed to allow a certain volume (capacitance) of fluid to slowlyincrease or decrease to a desired switching pressure level. However, itis difficult to repeat such pressures, and elaborate circuitry isusually required to provide the necessary repeatability. Another type ofknown timer comprises a fluidic oscillator combined with complex digitalcounter stages, and this configuration also has obvious drawbacks.

In the present invention accurate and relatively simple timers areprovided wherein each of the timing devices 74 and 80 comprises a logiccircuit 74A and 80A, and a bellows device 748 and 808, respectively.When the flip flop 60 is switched to provide an inspiration commandalong the conduit 62 the logic circuit 80A provides a regulated pressureoutput coupled through an orifice 80C to the chamber of the bellowsdevice 808, and causes the bellows element thereof to collapse. A rod80D is fixed to the moveable portion of the bellows element, and ismounted to engage a sensor E for causing a back pressure along a conduit80F which is connected as an inspiration cycle terminating signal of theflip flop 60. Similarly, the timing device 74 has the input of its logiccircuit 74A connected for actuation by the opposing output of the flipflop 60 while the sensor device 74E couples a signal along the conduit74F to terminate the exhalation cycle of the apparatus by switching theflip flop 60. Additionally, the ad justable orifice is connected inparallel with the orifice 80C to vary the [IE ratio as described above.

Various additional details of the construction of the valving apparatusare shown in FIGS. 3-7. Particularly, FIG. 3 shows an embodiment of thevalve construction utilized with the bellows apparatus 10 wherein theroom air is drawn through the filter 40, the oxygen/air mixture iscontrolled by the valve knob 44A, and the patient output hose isconnected to the output port 28A. The internal configuration of thevalve apparatus is shown in FIGS. 4-6 which comprise sectional viewswherein the opening 140, as shown in FIG. 4, comprises the port openingof the bellows element 12, while the input check valve 24 is shown incommunication with a duct 22 corresponding with the duct 22 illustratedin FIGS. 5 and 6. Similarly, the air filter 40 is also shown in FIG. 4,and the duct 16, communicating with the bellows chamber 14 and valve 42,is shown in FIG. 5. Also, the adjustable flow control orifice 52, andthe oxygen filter 54 are shown in FIG. 6, while the valve stem for themixing valve 44 is shown as element 448 in FIGS. 5 and 7. When the valvestem 44B is rotated by means of the valve knob 44A to its extremecounterclockwise position, all of the oxygen forced out of the chamber14 by the expanding bellows element 12 is vented to the atmospherethrough a vent opening 142 as illustrated in FIG. 3. As the knob 44A isrotated clockwise, however, increasing quantities of oxygen arepermitted to flow through the conduit 22, first through a slit portion44C in the valve stem 44B, and then through the full open orifce 44Dthereof so that when the valve knob 44A is turned completely clockwise,the entire quantity of oxygen forced out of the chamber 14 is drawn intothe bellows element 12. The bladder elements 26A and 42A shownrespectively in FIGS. 4 and 5 are controlled by the pressure signalscoupled through conduits 68 and 66, respectively, as described above inconjunction with FIG. 1.

Since the oxygen/air mixture is effected by the expanding bellows, andproportioned by the valve 44, the oxygen concentration is unaffected bythe patients breathing, the inspiratory flow rate, the tidal volume, thepatient hose pressure, or the cycle time, thereby providing anaccurately controllable system in this regard.

The timing devices 748 and 808, shown schematically in FIG. 2, areillustrated in FIG. 8, wherein the device 74B, is depicted in apartially sectional view. The timing devices include sealed cannisters150, 151, each having a sealed collapsible bellows device 152 mountedtherein. As shown, the sensor device 74E is supported on a spring 154and its elevation position is determined by the pressure exerted thereonby a cam 156 mounted on a shaft 158. Similarly, the sensor device 80E ispositioned by a corresponding cam 160 mounted on the shaft 158. In theoperation of the timers, a regulated air pressure is selectively appliedthrough one of the orifices 74C and 80C to the cannisters and 151. Then,

for example, if the cannister 150 is charged, the bellows 152 willcollapse causing the spring-loaded rod 74D attached thereto to moveupwardly untilvit engages the sensor 74E, thus closing a vent in theline 74F so that the flip flop 60 receives an input signal for switchingit to provide an inspiratory command along conduit 62 as shown in FIGS.1 and 2. The bellows 152 and the spring loading on the rod 74D. are soproportioned that the movement of the rod does not require a largepressure change, so that the travel time for the rod canbe accuratelyestablished. During calibration procedures, the adjustable orifice 120,as shown in FIGS. land 2 is completely closed, whereupon the cam 156 and160 are adjusted to provide the necessary exhalation and inspiratorytime periods so that the desired maximum value for the quantity I/E .isdefined. Then, the timing periods for both of the timers 74B and 80B canbe sis multaneously adjusted by rotating the shaft 158 to reposition thesensing devices 74E and 80E by means of the cams 156 and 160.Subsequently, the I/E ratio can be decreased by opening the valve 120 toa desired position.

The dump valves described above in conjunction with FIG. 2, are shown inFIG. 8, and a sectional view of the dump valve 74G is illustrated inFIG. 9 wherein it is seen that a bladder 162 maintains a valve seat 164in a closed position on a discharge opening in the side wall of thecannister 150. Then, when the master flip flop is actuated by theexhalation timer 74 to provide an inspiratory command along the outputconduit 62, the opposing output of the flip flop 60 is coupled to thebladder 162 to provide a slight negative pressure thereto so that theoxygen stored in the timer cannister 150 is exhausted to the atmospherethrough the port 166 by the released valve seat 164.

. The dump valve seals the outlet opening in the cannister 150 when theflip flop is switched out of its inspi-- ratory command state.

i In summary, the apparatus disclosedin the foregoing specification, andin the accompanying drawings, provides a patient ventilator which iscontrolled solely by fluidic circuitry to function manually,automatically, or semiautomatically, in response to the breathingrequirements of a patient.

- What is claimed is:

l. A fluidically controlled patient ventilator apparatus comprising:

a patient breathing hose;

means for supplying a predetermined quantitiy of air to the patientbreathing hose;

a fluidic flip flop circuit switchable into first and second states,said flip flop circuit having opposed input ports for controlling saidswitching, and having at least one output port providing a pressuresignal while said flip flop circuit is switched into said first stablestate;

means coupled between said flip flop circuit output port and said airsupply means to actuate the latter to supply air to the breathing hosein reponse to said pressure signal, thereby defining an inspiratoryperiod of operation;

a first fluidic timing means actuable during said inspi- ,ratory periodand a second fluidic timing means ac- .tuable during an exhalationperiod, said first and second timing means having respective outputports coupled;to said opposed input ports of said flip flop forcontrolling said flip flop to switch be tween said stable states,wherein an output signal from said first timing means actuates said flipflop to switch from its first to its second stable state, nd an outputfrom said second timing means actuates said flip flop to switch from itssecond to its first I stable state;

a fluidic trigger circuit having an input coupled to said patientbreathing hose for providing a trigger signal at an output port thereofin reponse to a minimum pressure in said patient breathing hosecorresponding to the termination of a patient exhalationcycle and meanscoupling said trigger signal to one of said input ports of said flipflop to control said flip flop to switch from its second to its firststable state to initiate said inspiratory period;

a fluidic pressure limit circuit having an input port coupled to saidpatient breathing hose for providing a limit signal at an output portthereof in reponse to a predetermined maximum pressure in the patientbreathing hose, andmeans coupling said limit signal to one of said inputports of said flip flop to control said flip flop to switch from itsfirst to its second stable state to terminate said inspiratory period;

a volume limit signal generating means coupled to said patient breathinghose for providing a trigger output signal in response to the sensing ofa predetermined quantity of air supplied to the patient breathing hoseby the air supply means, and means coupling said trigger signal to oneof said input ports'of said flip flop to control said flip-flop toswitch from its first to its second stable state to terminate saidinspiratory period;

and mode selecting means for selectively deenergizing said triggercircuit and said first timing means, one at a time.

2. A fluidically controlled patient ventilator apparatus as set forthin-claim 1 further comprising an adjustable oxygen/air mixing valvemeans coupled between said inlet valve and said bellows element forselective positioning-to control the oxygen content of the airwithin-the bellows, element wherein said mixing valve means is coupledto a source of room air, and is coupled through said inlet valve meansto a source of oxygen.

3. A fluidically controlled ventilator apparatus as set forth in claim 2wherein said bellows chamber comprises a fixed volume surrounding saidbellows element, and further comprising means responsive to saidpressure signal from said one output port of said flip flop circuit forcharging said bellows chamber with oxygen to collapse said bellows anddischarge the air therein through said outlet valve means;

said bellows element having a weight mountedtherein for causing itsexpansion upon depressurization of said bellows chamber; and furthercomprising conduit means interconnecting said bellows chamber and saidinlet valve means wherein said oxygen charged into said bellows chamberescapes through said inlet valve for selective coupling through saidmixing valve means to said expanding bellows element.

4. A fluidically controlled patient ventilator apparatus as set forth inclaim 1 wherein said flip flop circuit has a second output port forgenerating a pressure signal while said flip flop is switched into itssecond stable state defining an exhalation period of the apparatus,

and wherein said first and second timing means comprise respective firstand second fluidic logic switching circuits, first and second sealedcannisters, and first and second pressurized bellows members disposedwithin said sealed cannisters, said first switching circuit havingoutput port means coupled for actuation by the pressure signal from saidsecond output port of said flip flop circuit to charge a regulatedquantity of air into said first cannister, and said second switchingcircuit having output pot means coupled for actuation by the pressuresignal of said first output port of said flip flop circuit to chargesaid second cannister, wherein said charging of said cannisters causesthe bellows members therein to collapse, and first and second sensingmeans for generating said timing means output signals in response tosaid collapse of said respective bellows after a predetermined aircharging time of said cannisters, said sensing means being coupled tosaid opposed input ports of said flip flop circuits.

5. A fluidically controlled patient ventilator apparatus as set forth inclaim 4 wherein said first and second sensing means are movably mounted,and wherein movement thereof changes said predetermined air chargingtimes at which said output signals are generated, and further comprisinga rotatable shaft having a pair of cams mounted thereon in a spacedrelation for engaging said first and second sensing means, wherebyrotation of said shaft and cams moves said sensing means and changes thetiming periods of said first and second timing means.

6. A fluidically controlled patient ventilator apparatus as set forth inclaim 5 further comprising an adjustable by-pass valve connected tochange the charging time of said first cannister for independentlyadjusting the timing period of said first timing means.

7. A fluidically controlled patient ventilator apparatus as set forth inclaim 6 further comprising first and second dump valve means mountedrespectively on said first and second cannisters for depressurizing saidcannisters in response to input signals received respectively from saidsecond output port and said one output port of said flip flop circuit.

8. A fluidically controlled patient ventilator apparatus as set forth inclaim 1 wherein said trigger circuit and said pressure limit circuit areconstructed identically and comprise three proportional amplifiers connected in series, and three fluidic flip flops connected in series witheach other and in series with an output of said three fluidicamplifiers, and wherein said trigger circuit further comprises means forconnecting inputs of one of said three fluidic amplifiers to a pressuresource for adjusting the sensitivity thereof, and for connecting inputsof another one of said fluidic amplifiers to a positive end expiratorypressure signal and to said patient breathing hose.

9. A fluidically controlled patient ventilator apparatus as set forth inclaim 1 further comprising a positive end expiratory pressure circuithaving an output coupled to an input port of said patient triggercircuit for providing a bias signal thereto, said end expiratorypressure circuit including a fluidic capacitance having an output portcoupled as said input to said trigger circuit; an adjustable offsetpressure valve having an output coupled as an input to said fluidiccapacitance; a pressure actuated gate valve having an output coupled tothe input of said offset valve, having an input coupled to a source ofpositive end expiratory pressure sinals, and having a gate'input coupledfor actuation by said flip flop circuit during said inspiratory period.

10. A fluidically controlled patient ventilator apparatus as set forthin claim 1 further comprising first and second manually operablepressure switches connected respectively to said opposed inputs of saidflip flop for switching said flip flop from one of its stable states toits other stable state, and first, second and third indicatordisplaymeans coupled respectively to the outputs of said patient triggercircuit, said pressure limit circuit, and said first timing means forindicating the presence of signals at the outputs thereof.

1. A fluidically controlled patient ventilator apparatus comprising: apatient breathing hose; means for supplying a predetermined quantitiy ofair to the patient breathing hose; a fluidic flip flop circuitswitchable into first and second states, said flip flop circuit havingopposed input ports for controlling said switching, and having at leastone output port providing a pressure signal while said flip flop circuitis switched into said first stable state; means coupled between saidflip flop circuit output port and said air supply means to actuate thelatter to supply air to the breathing hose in reponse to said pressuresignal, thereby defining an inspiratory period of operation; a firstfluidic timing means actuable during said inspiratory period and asecond fluidic timing means actuable during an exhalation period, saidfirst And second timing means having respective output ports coupled tosaid opposed input ports of said flip flop for controlling said flipflop to switch between said stable states, wherein an output signal fromsaid first timing means actuates said flip flop to switch from its firstto its second stable state, nd an output from said second timing meansactuates said flip flop to switch from its second to its first stablestate; a fluidic trigger circuit having an input coupled to said patientbreathing hose for providing a trigger signal at an output port thereofin reponse to a minimum pressure in said patient breathing hosecorresponding to the termination of a patient exhalation cycle and meanscoupling said trigger signal to one of said input ports of said flipflop to control said flip flop to switch from its second to its firststable state to initiate said inspiratory period; a fluidic pressurelimit circuit having an input port coupled to said patient breathinghose for providing a limit signal at an output port thereof in reponseto a predetermined maximum pressure in the patient breathing hose, andmeans coupling said limit signal to one of said input ports of said flipflop to control said flip flop to switch from its first to its secondstable state to terminate said inspiratory period; a volume limit signalgenerating means coupled to said patient breathing hose for providing atrigger output signal in response to the sensing of a predeterminedquantity of air supplied to the patient breathing hose by the air supplymeans, and means coupling said trigger signal to one of said input portsof said flip flop to control said flip-flop to switch from its first toits second stable state to terminate said inspiratory period; and modeselecting means for selectively deenergizing said trigger circuit andsaid first timing means, one at a time.
 2. A fluidically controlledpatient ventilator apparatus as set forth in claim 1 further comprisingan adjustable oxygen/air mixing valve means coupled between said inletvalve and said bellows element for selective positioning to control theoxygen content of the air within the bellows, element wherein saidmixing valve means is coupled to a source of room air, and is coupledthrough said inlet valve means to a source of oxygen.
 3. A fluidicallycontrolled ventilator apparatus as set forth in claim 2 wherein saidbellows chamber comprises a fixed volume surrounding said bellowselement, and further comprising means responsive to said pressure signalfrom said one output port of said flip flop circuit for charging saidbellows chamber with oxygen to collapse said bellows and discharge theair therein through said outlet valve means; said bellows element havinga weight mounted therein for causing its expansion upon depressurizationof said bellows chamber; and further comprising conduit meansinterconnecting said bellows chamber and said inlet valve means whereinsaid oxygen charged into said bellows chamber escapes through said inletvalve for selective coupling through said mixing valve means to saidexpanding bellows element.
 4. A fluidically controlled patientventilator apparatus as set forth in claim 1 wherein said flip flopcircuit has a second output port for generating a pressure signal whilesaid flip flop is switched into its second stable state defining anexhalation period of the apparatus, and wherein said first and secondtiming means comprise respective first and second fluidic logicswitching circuits, first and second sealed cannisters, and first andsecond pressurized bellows members disposed within said sealedcannisters, said first switching circuit having output port meanscoupled for actuation by the pressure signal from said second outputport of said flip flop circuit to charge a regulated quantity of airinto said first cannister, and said second switching circuit havingoutput port means coupled for actuation by the pressure signal of saidfirst output port of said fLip flop circuit to charge said secondcannister, wherein said charging of said cannisters causes the bellowsmembers therein to collapse, and first and second sensing means forgenerating said timing means output signals in response to said collapseof said respective bellows after a predetermined air charging time ofsaid cannisters, said sensing means being coupled to said opposed inputports of said flip flop circuits.
 5. A fluidically controlled patientventilator apparatus as set forth in claim 4 wherein said first andsecond sensing means are movably mounted, and wherein movement thereofchanges said predetermined air charging times at which said outputsignals are generated, and further comprising a rotatable shaft having apair of cams mounted thereon in a spaced relation for engaging saidfirst and second sensing means, whereby rotation of said shaft and camsmoves said sensing means and changes the timing periods of said firstand second timing means.
 6. A fluidically controlled patient ventilatorapparatus as set forth in claim 5 further comprising an adjustableby-pass valve connected to change the charging time of said firstcannister for independently adjusting the timing period of said firsttiming means.
 7. A fluidically controlled patient ventilator apparatusas set forth in claim 6 further comprising first and second dump valvemeans mounted respectively on said first and second cannisters fordepressurizing said cannisters in response to input signals receivedrespectively from said second output port and said one output port ofsaid flip flop circuit.
 8. A fluidically controlled patient ventilatorapparatus as set forth in claim 1 wherein said trigger circuit and saidpressure limit circuit are constructed identically and comprise threeproportional amplifiers connected in series, and three fluidic flipflops connected in series with each other and in series with an outputof said three fluidic amplifiers, and wherein said trigger circuitfurther comprises means for connecting inputs of one of said threefluidic amplifiers to a pressure source for adjusting the sensitivitythereof, and for connecting inputs of another one of said fluidicamplifiers to a positive end expiratory pressure signal and to saidpatient breathing hose.
 9. A fluidically controlled patient ventilatorapparatus as set forth in claim 1 further comprising a positive endexpiratory pressure circuit having an output coupled to an input port ofsaid patient trigger circuit for providing a bias signal thereto, saidend expiratory pressure circuit including a fluidic capacitance havingan output port coupled as said input to said trigger circuit; anadjustable offset pressure valve having an output coupled as an input tosaid fluidic capacitance; a pressure actuated gate valve having anoutput coupled to the input of said offset valve, having an inputcoupled to a source of positive end expiratory pressure sinals, andhaving a gate input coupled for actuation by said flip flop circuitduring said inspiratory period.
 10. A fluidically controlled patientventilator apparatus as set forth in claim 1 further comprising firstand second manually operable pressure switches connected respectively tosaid opposed inputs of said flip flop for switching said flip flop fromone of its stable states to its other stable state, and first, secondand third indicator displaymeans coupled respectively to the outputs ofsaid patient trigger circuit, said pressure limit circuit, and saidfirst timing means for indicating the presence of signals at the outputsthereof.